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Seats, Seatbelts, and Warning

UPDATED 11/2022



The parts books refer to USA and Canadian cars having cloth seats. However, this is not accurate. All USA/Canadian cars were only equipped with leather; black or brown. 


The front passenger seat on most 1972 and all 1973 SM’s intended for North America had a weight sensing switch for the seat belt buzzer system.  The switch was P/N 5422171, made by Torrix. There will be more about the seat belt warning system below. 

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Seat belts in the late 1960's and 1970's tended to have gangly, unsatisfactory designs that were difficult to adjust, got tangled in the seats, and slammed in the doors. SM's were no exception to these issues. 


Seat belt requirements were driven by Federal Motor Vehicle Safety Standard (FMVSS) #209, "Seat Belt Assemblies."


Most Euro SM’s had non-retractable, manually-adjusted 3-point seat belts. 


USA/Canadian seat belt configurations were as follows:


  • All 1971 SM's and 1972 SM’s that were manufactured in calendar year 1971 had three-point non-retractable, manually-adjusted seat belts (front and rear). We have seen two manufacturers; the most common one was a British company called Britax who also provided similar seat belts for USA DS's, but I found a few SM's with a second manufacturer, a Finnish company called Klippan. 


  • All 1972 SM’s that were manufactured in calendar year 1972 and all 1973 USA/Canadian SM’s had inertia reel seat belts. The front inertia reels had an electrical wire that was used for the seat belt warning light logic. Rear seat belts were inertia reel (lap belt only) with no warning light. The front inertia reel belts had clip-in shoulder harness straps that could be used (or not). 


The inertia reel seat belts used on USA/Canadian cars do not show up in the parts books. We have been told that the cars had provisions for the inertia reels built into them in the factory, but the inertia reel seat belts themselves were installed once the cars were in North America (i.e. port installed parts). We have been unable to confirm this, but it is plausible, especially since the same seat belts were used in some American Ford cars of the era (the inertia reel design is referred to in Ford circles as "starburst" belts due to the pattern on the buckle). 

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Britax "Lyfe-Lok" manual 3-point seat belts as found on most USA SM's with manufacturing dates in 1971

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USA/Canada style inertia reel seat belts as found on 1972 SM's manufactured in 1972 and on all 1973's. These were found on some Ford cars of the era (note the starburst pattern on the buckle).

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US regulations of the era required that all cars have a warning system that had a visual and aural indication if seat belts were not buckled when that particular seat was occupied. This rule was mandated for 1972 (front seats only), and as a result, both DS's and SM's had such systems added for cars manufactured in 1972. 


USA/Canadian SM's went through a progression of changes to the seat belt warning system. The warning system consisted of a flashing light on the dash that read, “FASTEN SEAT BELTS” and a steady buzzer that sounded if the front seat belt(s) were not buckled. The incorporation dates of the various versions of the seat belt warning light are a bit confusing, but we think we have untangled it:


  • 1971 USA/Canadian SM's were equipped with standard, manually adjustable seat belts and no warning system.

  • 1972 USA/Canadian SM’s that were manufactured in calendar year 1971 were equipped with standard, manually adjustable seat belts and no warning system


  • 1972 USA/Canadian SM’s that were manufactured in calendar year 1972 had inertia reels, the warning system, and a FASTEN SEAT BELT light mounted vertically on the dashboard facia. 

  • 1973 USA/Canadian SM’s had inertia reels and the warning system, but now with the seat belt light on the main dash facia turned 90 degrees (now horizontal) adjacent to a relocated hazard switch and hazard indication light. 

USA/Canadian SM’s manufactured in calendar year 1971 had no seat belt warning system

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1972 USA/Canadian SM’s manufactured in calendar year 1972 with vertical seat belt light

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Model year 1973 USA/Canadian SM’s with horizontal seat belt light and relocated hazard switch/light

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For cars with the FASTEN SEAT BELT light, the front passenger seat had a weight switch to indicate when someone is sitting on it as part of the seat belt light / buzzer logic. The logic to turn on the flashing FASTEN SEAT BELT light and the steady buzzer was:


weight in a front seat (passenger side only) + parking brake released + ignition on + front seat belt not buckled = fasten seat belt light (flashing) and buzzer (steady)


For the driver's seat, the logic is the same except the driver's seat didn't have the seat weight switch installed since it can be assumed someone will always be sitting in that seat when the car is being driven. The very weird seat weight switch in the front passenger seat can be seen in the DS section HERE. A schematic of the seat belt wiring system can be found in the SM WIRING section. 


The seat belt buzzer was P/N 5423970, make by Saker. 

FASTEN SEAT BELT LIGHT, Horizontal version as used on 1973's, made by TORRIX


Wiring located under the front pasengerseat that is used for the seat weight sensing switch. This wiring is on all North American SM's manufactured in calendar year 1972 and all 1973's


Demonstration of the flashing FASTEN SEAT BELT light and the super annoying seat belt buzzer 

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